The present invention can find applications related to relaying aspects for communication via a mobile device used as a relay node in a network, such as, for example a 3GPP LTE network.
LTE (for “Long Term Evolution”), marketed as 4G LTE, is a standard for wireless communication of high-speed data for mobile phones and data terminals. It is based on older network technologies (such as the universal mobile telecommunication system (UMTS)), increasing the capacity and speed using a different radio interface together with core network improvements. Optimized components from the UMTS used in the LTE are signalled by the prefix “evolved”. For example, a base station transmitting communications as a NodeB in the UMTS is called an “eNodeB” in the LTE.
Such an evolution has an influence on the communication protocol layers stack also. In the 3GPP LTE network, it can be spitted into seven different layers constituting the Open Systems Interconnection (OSI) model. It is recalled that an OSI model is a prescription of characterizing and standardizing the functions of a communications system. Similar communication functions are grouped into logical layers. A layer serves the layer above it and is served by the layer below it.
Every layer has to offer the upper layers the service of information transmission between a user equipment (UE) and the network. Therefore, upper layers need channels from the lower layers to communicate with the UE. For example, Layer 3 offers higher layers channels that are called radio bearers (RB) for the transfer of network data. Network data can be either control data for the configuration of the network or user data (for example telecommunication data). Layer 2 offers logical channels onto which radio bearers can be mapped. Therefore, the service access points between Layer 2 (reference “L2” in FIG. 3) and upper layers are RBs. A more detailed description of such OSI layers will be given with respect to FIG. 3 presented hereafter.
In fact, FIG. 2 illustrates a structure of a radio interface protocol between the terminal and the E-UTRAN according to the 3GPP radio access network standards. As shown in FIG. 2, the radio interface protocol has vertical layers including a physical layer, a data link layer, and a network layer, and has horizontal planes including a user plane (U-plane) for transmitting user data and a control plane (C-plane) for transmitting control information.
The user plane is a region that handles traffic information with the user, such as voice or Internet protocol (IP) packets. The control plane is a region that handles control information for an interface with a network, maintenance and management of a call, and the like.
The protocol layers in FIG. 2 can be divided into a first layer (L1), a second layer (L2), and a third layer (L3) based on the three lower layers of an open system interconnection (OSI) standard model. The first layer (L1), or the physical layer, provides an information transfer service to an upper layer by using various radio transmission techniques. The physical layer is connected to an upper layer, called a medium access control (MAC) layer, via a transport channel.
The MAC layer and the physical layer exchange data via the transport channel. The second layer (L2) includes a MAC layer, a radio link control (RLC) layer, a broadcast/multicast control (BMC) layer, and a packet data convergence protocol (PDCP) layer.
The MAC layer handles mapping between logical channels and transport channels, and provides allocation of the MAC parameters for allocation and re-allocation of radio resources. The MAC layer is connected to an upper layer, called the radio link control (RLC) layer, via a logical channel.
Various logical channels are provided according to the type of information transmitted. In general, a control channel is used to transmit information of the control plane, and a traffic channel is used to transmit information of the user plane.
A logical channel may be a common channel or a dedicated channel depending on whether the logical channel is shared. Logical channels include a dedicated traffic channel (DTCH), a dedicated control channel (DCCH), a common traffic channel (CTCH), a common control channel (CCCH), a broadcast control channel (BCCH), and a paging control channel (PCCH) or a shared channel control channel.
The BCCH provides information including information utilized by a terminal to access a system. The PCCH is used by the UTRAN to access a terminal.
In a 3GPP LTE network, a network node such as the evolved NodeB (eNB) has the role of transmitting/receiving the data and signalling from the core network (CN) to the User Equipments (UEs) which are under its radio cell coverage, or from the UEs to CN. A user equipment (UE) is a terminal such as a telephone, a smartphone, a connected computer, a tablet, etc.
FIG. 1 gives an overview of the network between the UE and the CN. Furthermore, UEs need to transmit/receive data and/or signalling to/from the eNB whenever a communication is required (e.g. to register, update registration, establish a data session or a voice call). For example, in FIG. 1, UEA1 and UEA2 are located within cell A and are therefore using eNBA to communicate with the network.